Serotonin, dopamine, and norepinephrine are known to be important chemical messengers participating in the transmission of nerve impulses in the brain. These messengers are liberated at specific sites on pre-synaptic cells and received, to complete transmission of the impulse, at specific sites on post-synaptic cells. Their effect is then terminated by metabolism or by uptake into the pre-synaptic cells. Drugs capable of blocking the pre-synaptosomal uptake of either of these chemical messengers in the brain, are useful in alleviating disorders associated with decreased levels of these chemical messengers. For example, duloxetine and fluoxetine which are known serotonin reuptake inhibitors have been found to be useful in the treatment of depression, obesity and obsessive-compulsive disease (Wong, et al., U.S. Pat. No. 5,532,244). Also, Moldt, et al., U.S. Pat. No. 5,444,070, discloses the use of dopamine reuptake inhibitors in the treatment of depression, Parkinsonism, drug addiction and/or abuse, cocaine and/or amphetamine addiction and/or abuse. Freedman, et al., U.S. Pat. No. 6,136,803 also discloses synaptic norepinephrine or serotonin uptake inhibitors which are useful in treating depression in a patient. Furthermore, Norden, U.S. Pat. No. 5,789,449 discloses the use of serotonin re-uptake inhibitors in treating psychiatric symptoms consisting of anger, rejection sensitivity, and lack of mental or physical energy. Also, Foster, et al., U.S. Pat. No. 4,902,710, discloses the use of serotonin and norepinephrine uptake inhibitors in suppressing the desire of humans to smoke or consume alcohol. Thus, there continues to remain a need to develop novel compounds which block reuptake of norephinephrine, dopamine or serotonin.
Compounds which inhibit the reuptake of serotonin or norephinephrine, have also been used in combination therapy. For example, Glatt, et al., U.S. Pat. No. 6,121,261 discloses the use of selective serotonin reuptake inhibitors or norephinephrine uptake inhibitors, in combination with neurokinin-1 receptor antagonist for treating attention deficit disorder in a patient.
Also, Hohenwarter, U.S. Pat. No. 4,843,071 discloses the use of a norepinephrine re-uptake inhibitor and a norepinephrine precursor in the treatment of obesity, drug abuse, or narcolepsy in a patient. Furthermore, Wong, et al., U.S. Pat. No. 5,532,244, discloses the use of serotonin reuptake inhibitors in combination with a serotonin 1A receptor antagonist, to increase the availability of serotonin, norepinephrine and dopamine in the brain.
The treatment of a variety of neurological and psychiatric disorders is characterized by a number of side effects believed to be due to the compounds' inability to selectively block certain neurochemicals, and not others. ADHD, for example, is a disease affecting 3-6% of school age children, and is also recognized in a percentage of adults. Aside from hampering performance at school, and at work, ADHD is a significant risk factor for the subsequent development of anxiety disorders, depression, conduct disorder and drug abuse. Since current treatment regimes require psychostimulants, and since a substantial number of patients (30%) are resistant to stimulants or cannot tolerate their side effects, there is a need for a new drug or class of drugs which treats ADHD and does not have resistance or side effect problems. In addition, methylphenidate, the current drug of choice for the treatment of ADHD, induces a number of side effects; these include anorexia, insomnia and jittery feelings, tics, as well as increased blood pressure and heart rate secondary to the activation of the sympathetic nervous system. However, Methylphenidate also has a high selectivity for the dopamine transporter protein over the norepinephrine transporter protein (DAT/NET Ki ratio of 0.1), which can lead to addiction liability and requires multiple doses per day for optimal efficacy. Thus, there continues to remain a need to develop novel compounds which block reuptake of norephinephrine, dopamine, and serotonin with particular selectivity ratios.
U.S. Pat. No. 3,947,456, discloses tetrahydroisoquinolines which are said to have utility as anti-depressants. U.S. Pat. No. 3,666,763, describes the use of phenyl tetrahydroisoquinoline derivatives as antidepressants and antihypotensives. Canadian Patent Application No. 2,015,114, discloses the use of phenyl tetrahydroisoquinoline derivatives as antidepressants; moreover, described therein are apparently nonselective as to norepinephrine, serotonin, and dopamine uptake. UK Patent Application No. 2,271,566, discloses the use of phenyl tetrahydroisoquinoline derivatives as anti-HIV agents. PCT International Application No. WO98/40358 discloses the use of phenyl tetrahydroisoquinoline derivatives to be useful in the treatment of disorders of glucose metabolic pathways. WO97/36876 discloses the use of phenyl tetrahydroisoquinoline derivatives as anticancer agents. WO97/23458 also describes 4 phenyl-substituted tetrahydroisoquinolines as NMDA receptor ligands useful for conditions associated with neuronal loss. Phenyl-substituted tetrahydroisoquinolines are also described in Mondeshka et al I1 Farmaco, 1994, 49 pp. 475-481.
Nomofensine® which is a 4 phenyl-substituted tetrahydroisoquinoline derivative is known to inhibit the neuronal uptake of dopamine and other catecholamines and has shown clinical efficacy for ADHD. However, long term administration of Nomofensine® results in fatal immune hemolytic anemia. Thus, there continues to remain a need to develop novel compounds which treat ADHD but do not have the serious side effects associated with Nomifensine® or the currently prescribed psychostimulants.
The present invention discloses novel aryl and heteroaryl substituted tetrahydroisoquinoline derivatives compounds which block reuptake of norepinephrine, dopamine, or serotonin, and are useful as alternatives to methylphenidate, and known psychostimulants, in the treatment of ADHD and other neurological and psychiatric disorders.
The present inventors have discovered that the claimed compounds which block reuptake of norepinephrine, dopamine, and serotonin with particular selectivity ratios, e.g., being more selective for the norepinephrine transporter (NET) protein than dopamine transporter (DAT) protein or serotonin transporter (SERT) protein (lower Ki for NET than for DAT and SERT). It is postulated that the compounds would therefore be effective as an ADHD treatment with reduced addictive liability profiles. In particular, some of the compounds of this invention are surprisingly and particularly selective for NET over the SERT protein, thus also affording compounds without the known side effect profiles of the selective serotonin reuptake inhibitor (SSRI) class of compounds.